1. Field of the Invention
The present invention relates to an electronically controlled fuel injection apparatus for an internal cumbustion engine, and more particular to an improvement of an electronically controlled fuel injection apparatus for an internal combustion engine suitable for use in an internal combustion engine of an automobile having an air conditioning device, which apparatus determines the amount of fuel injection in accordance with engine operating conditions such as an engine rotation speed and the amount of intake air and, in a deceleration operation, cuts the fuel injection until the engine rotation speed falls below a predetermined fuel injection reinitiation rotation speed if the current engine rotation speed is higher than a predetermined fuel injection cut rotation speed.
2. Description of the Prior Art
As apparatus for supplying air-fuel mixture having an optimum air-fuel ratio in accordance with operating conditions of an internal combustion engine to a combustion chamber of the engine, apparatus which uses an carburetor and apparatus which uses a mechanically or electronically controlled fuel injection apparatus have been known. In recent years, the electronically controlled fuel injection apparatus has been widely used because it can supply air-fuel mixture having a correct air-fuel ratio to an engine of an automobile which requires purification measures for exhaust gas. In a prior art internal combustion engine having such an electronically controlled fuel injection apparatus, the fuel injection is cut in a deceleration operation until an engine rotation speed falls below a predetermined fuel injection reinitiation rotation speed if the current engine rotation speed is higher than a predetermined fuel injection cut rotation speed in order to prevent after-fire, save fuel and prevent exhaust of incomplete combustion gas. The fuel injection reinitiation rotation speed is set in addition to the fuel injection cut rotation speed in order to provide a hysteresis function to the stop of the fuel injection to prevent undesired condition such as hunting from occurring. In the prior art electronically controlled fuel injection apparatus, however, the fuel injection is stopped even when a compressor of a car air conditioner is driven by an engine output shaft into an active state and the amount of intake air when a throttle valve is fully closed is increased by an air bypass valve of a throttle body in order to maintain necessary output for the compressor of the air conditioner. Accordingly, in the deceleration operation when the air conditioner compressor is active, a torque generated by the engine immediately before the stop of the fuel injection is large and a friction torque immediately after the stop of the fuel injection is large. Since a difference between the positive and negative torques is large, the drivability is very poor and a shock occurs upon the stop of the fuel injection.
In the prior art electronically controlled fuel injection apparatus, the fuel injection is stopped until the engine rotation speed falls below the predetermined fuel injection reinitiation rotation speed if the current engine rotation speed is higher than the predetermined fuel injection cut rotation speed in order to prevent the hunting, as described above. If the engine rotation speed is higher than the predetermined fuel injection cut rotation speed, the operation mode moves to the deceleration mode. If the deceleration mode resumes if it has been interrupted intermediate the fuel injection cut rotation speed and the fuel injection reinitiation rotation speed, the fuel injection is stopped until the engine rotation speed falls below the fuel injection reinitiation rotation speed. Accordingly, the prior art apparatus has problems in the drivability of car when it is accelerated or decelerated during the deceleration mode.